Arc incandescent electric lamp



E. A. GIMINGHAM.

ARC INCANDESCENT ELECTRIC LAMP.

APPLICATION flLED OCT-15, I915.

Patented Apr. 12, 1921.

UNITED STATES PATENT OFFICE.-

EDWARD ALFRED GIMINGHAM, OF LONDON, ENGLAND.

ARC INCANDESCENT ELECTRIC LAMP.

Specification of Letters Patent.

Patented Apr. 12, 1921.

Application filed October 15, 1915. Serial No. 56,016.

cent Electric Lamps, of which the following is a specification.

This invention relates to improvements in arc incandescent lamps, thatis to say lamps which have substantially the outward appearance andconstruction of the ordinary incandescent electric lamp and a bulb whichis of such form and is so closed as to allow of its being properlyexhausted; while the lamp is furnished with means for forming ormaintaining an are within the bulb between two poles of tungsten orother suitable highly refractory material, such means being of simpleconstruction which will allow of the complete exhaustion of all oxygenfrom the bulb. In hitherto known constructions of lamps with tungstenpole ieces in an inclosed globe the poles have een moved apart or heldapart by mecha-- nism within the globe which have made completeexhaustion impossible. The invention relates more particularly to lamps'of the type specified which after exhaustion are filled with an inertgas such as nitrogen or argon for example. A minute quantity of oxygenmay be constantly supplied within the lamp by heating some suitablesubstance such as barium chlorate byexposing it to the heat ofthe are.This facilitates gthe starting of the are.

' In one constructioirof nitrogen filled lamp passing of the, typereferred to two poles of electrodes are fixedf'permariently apart'andthe in orhood foi the oles "lS ionipedf by a heater ,,'where=f' .a arcan readily. be formedbetweeng r,

' terminates {in an electr u ent. t r n upon = 'the-;poles=.with j,lowtension currents asP-com-t monly 'in use for ordinary lighting.According to the present invention, the heater which serves to ionizethe gases also serves to carry one pole of the arc and, on ionizationbeing completed, the arc is formed between an electrode in parallel withone end of the heater and a point on the heater or an electrode inarallel with the other end of the heater. ccording to one form'of thisinvention the heater is arranged in close proximity to one electrode andit has upon it a shield, of tungsten for example, at a point suitable toform another electrode, so that an arc of the desired size may be formedbetween the two electrodes. The heater therefore serves first as inionizer and then at one point as one of the electrodes. In-

stead however of the shield above referred to being actually formed uponthe heater, it may be carried upon one of the leading in wlres of theheater so as to be electrically in one piece therewith, and in suchproximity thereto that the gas between the electrodes is properlyionized. In either case the current passed through the heater for thepurpose of ionizingthe gas and start: ing the arc-is cut off, eitherautomatically or by a hand operated switch, after a few moments, andthecurrent then passes from one electrode to the other across the arc gap.

The invention as applied to a lamp on a di- In the construction shown inFig.' 1, three leads A, B, C, are introduced into a globe D,-containingan inert gas. by means of the ordinary-"Edison stem. Outside the globes'A andBareconnected-together' 1 f lead, and the connectBdthrough tnitable re- I The-lead h gnrhe stem and Oils-E, of tungsten.

the-"tWfe'lead 7 wan-the molybdenum or other suitable highly re- Theother lead A, terminates in an expansion strip F, (formed fractorysubstance.

for example of two metal strips having different co-efi'icients ofexpansion such as molybdenum and nickel or molybdenum and nickel copperalloy fused together) the head of which F normally'makes contact with ahead G on a lead A carried by an extension of the Edison stem. The lowerend of the lead A is connected with one end of the heater H, which islooped and at its other incandescent will end joins the lead 0. Aroundthe end of the heater H which is nearest to the elec trode E is arrangeda spiral I of stout wire, of tungsten for example, which is secured to Ithe lead C at the same point as the heater H.

The operation of the lamp is as follows The current passes through theleads A, A and the expansion strip F, tothe heater H and thence to thelead C. Immediately the heater is incandescent the gas between it andthe posit-ive pole is ionized and a small current passes between thepole E and the heater. Upon the expansion strip becoming heated by thehot gas rising from the heater it warps and breaks the contact between Fand G. This has the effect of allowing the current at the full potentialof the external supply to operate in breaking down the resistance of theare gap, and the current forming the arc flows by means of the lead Bthrough the electrode E across the gap to the coil or shield I. Thecurrent now passes no longer through the heater H proper. The heater Hand the shield I are however practically one, as they are both carriedby the end of the lead C, this being one convenient method of mountingthe shield instead of directly on the heater H.

In the arrangement of heater and electrodes shown in Fig. 2 theelectrode E is a solid sphere of fused tungsten, which when ivepractically equal illumination in all directions, and the heater Hbetween the leads A and C- is straight and. has a thickened portion I oftungsten for example to serve as protection and form the negativeelectrode in the middle.

In the arrangement shown in Fig. 3 the ionizer H is also straight, buthere it is surrounded by a coil I as in Fig. 1 serving as a shieldandforming the negative electrode. The ositive electrode E is here againof the flat orm shown in Fig. 1.

In Fig. 4 is shown another arrangement, somewhat similar to that of Fig.2, but having an additional device for insuring that the arc shall burnbetween the actual thickened or heavy portions forming the electrodes E,I. The positive electrode E in the form of a sphere is carried upon aportion B of the lead B, which is connected with the lead .B

by an expansion strip K. On the are being struck in the manner describedin connection with Fig. 1, the expansion strip warmed by the heatconducted from the hot electrode the electrode E and the heater H,instead of between E'and the thickened portion I, owing toithe latterbeing less hot than the heater of smaller section. I The mdvement of theelectrode E toward the negative elecare with it until it is maintainedbetween E and I as desired.

This expansion strip may be set at such an angle with the heater thatwhile the arc is drawn along to. the desired position between E and .I,the length of the arc gap is also increased. Such an arrangement enablesthe electrode to be placed nearly touching the heater when the lamp isout and facilitates the starting of the are by reason of the short gapto be ionized. By careful construction of the ex ansion strip anydesired length of arc ma be formed.

In Fig. .5 is shown a positive electrode in the form of a hollow spherehaving a thickened portion which is intended to act as a protectionagainst premature burning through at the point of arcing. This form maybe made in two or more parts fused together. The two halves are moldedand the edges held together and fused in an electric are for example. Bycareful construction of the thickened portion the whole surface of thesphere is by conduction brought to approxlmately uniform temperature,

1 The electrode shown in Fig. 6 has fiat surfaces and is triangular insection; such an electrode would when incandescent throw the maximumbeam in a direction at right angles to its largest fiat surface, the arestriking at the apex of the triangular shaped electrode."

The electrode may also be rectangular in section, as in Fig. 1, in whichcase the maximum beam will be in a direction at right angles to the faceopposite that on which the arc strikes.

In Fig. 7 is shown a lamp similar in construction to that shown in Fig.1, but furnished with a tube L in position and containing bariumchlorate orsimilar chemical which at thetemperature of the lamp when aburning gives off a minute quantity of o xygen. It is found that thisdevice assists the The ogygen attacks.

formation of the arc. the surfaces of the electrodes on cooling. IWhenthe lamp is again started the slight film of oxid formed on theelectrodes is easily volatilized by the passing of the current. It isthis action apparently which assists in breaking down the resistance ofthe arc gap. Probably the resistance of the around the electrodes is'lowered,by the dis turbing action of the volatilized particles of oxid,and the arc is thus more easily established. The presence of the oxid'cannot be detected with the naked .eye, but its presence on theelectrodes is established by the momentary wandering of the are when thelam is restarted. The volatilized oxid is not in sufficientquantity todiscolor the bulb ofthe lamp, such thin films which may be deposited onthe glass being white in color.

In this figure the lead C is shown furnished with a sleeve of silica M.This has been found to be of advantage when there is any tendency forthe arc to run up the leads. The lead B may also be so protected ifrequired. In mercury vapor. lamps a quartz sleeve has been usedsurrounding the lead in wire passing through a body of mercury andcarrying the anode, so that the arc may. not run to the mercury.

Instead of the expansion strip break F, F, G described, any otherconvenient form of break, such as a magnetic break may be employed. Theare may if desired be started by means of a hand operated switch outsidethe lamp.

It is very necessary thatthe lamp should be thoroughly exhausted of alltracesof water vapor, and gases occluded by the elec trodes and leadsbefore the inert gas is admitted.

The heater or ionizer H may consist of tungsten or molybdenum wire, orof tungsten mixed or in combination with refractory earths such aszirconia, thoria, calcium oxid, titanium oxid, tantalum oxid, or otherhighly refractory substances. Some of these refractory oxids possess theproperty of ionization to a very high degree when heated. For example, asatisfactory ionizer may be made by mixing zirconia and tungsten inequal parts and forming same into threads or filaments by any of thewell known methods.

of obtaining light-giving bodies but in carrying out this invention theobject is not to carry the process of reduction too far but, to maintainas far as possible within the filament the ionizing properties of therefractory earths, so that the repeated striking of the arc by means ofthe ionizer during the life of the lamp may be possible. Filaments suchas those mentioned above, in which refractory oxids are present in anyquantity, are not efficient light giving bodies, as their surfaces whenviewed under the microscope show them to be dull and irregular, but theyare active ionizers at a much lower temperature than similar filamentsconstructed of pure metals such as tungsten or molybdenum.

In the construction of the ionizer from mixtures of tungsten-andrefractory earths, the well known method of using a carbon binder may beemployed, which can be removed later by the passing of a current in anatmosphere of hydrogen or other reducing gas, or as only short thickfilaments are rerequired they maybe formed without the addition of acarbonaceous binder.

The ionizer may be straight or spiral or may be mounted in the form of aloop, having thev protection acting as the negative electrode, commonwith the negative pole of the ionizer as illustrated in Figs. 1 and 3,or

Similar filaments have been previouslyconstructed with the object it maybe straight, having as in Figs. 2 and 4 a protection acting as thenegative electrode in the center of the ionizer. The negative electrodemay be of hammered or drawn tungsten or an suitable'refractoryconductor. In. fact t e same refractory materials may be used for boththe ionizer and the protection acting as the negative electrode. Theionizer may be of such dimensions that no protection is required at thepoint of arcing. It is, however, desirable that the ionizer should beused as far as possible only as a means of starting the arc.

The shield on the heater may also be produced by burning the are at ahigh current density until a sufficient quantity of sputtered metal hasbeen deposited on the surface of the ionizer. sputtered metal is atriangular needle and offers good protection to the ionizer at the pointof arcing, besides assisting in strikingp the arc at a normal current.rect current lamps the major portion of the light of the lamp isobtained, may be constructed of fused tungsten or tungsten alloyed withother refractory metals, or tungsten mixed or in combination withrefractory earths such as those specified above for use in theconstruction of the ionizer or. negative electrodes. By suitablyarranging.

the ionizer the positive electrode may be wholly constructed from afused oxid such as zirconia,which is a non-conductor when cold, butwhich when heated conducts electricity.

These positive electrodes may be formed in any desired shape, and may beso arranged in the lamp that the maximum illumination is thrown in anydesired direction.

A satisfactory arc may be maintained at a pressure of approximately 1}an atmosphere but I wish it to be understood that the arc may be startedand maintained at pressures of gas as low as approximately th of anatmosphere or even lower to pressure of 1 atmosphere or higher.

What I claim as my invention is 1. In an electric arc incandescent lampa bulb containing an inert gas, a heater adapted to ionize the'gas, anelectrode in parallel with one end of the heater, and a second Eachparticle of the electrode surrounding a portion of therent has beenpassed, the other electrode being'electrically connected with the heaterand being, at least in part, interposed between the first electrode andheater.

4. In an electric arc incandescent lamp, a bulb containing an inert gas,a heater adapted to ionize the gas, an electrode in parallel with oneend of the heater, and having means adapted to move it relatively to theother electrode upon a current passing, the other electrode beingcarried by the heater.

5. In an electric arc incandescent lamp, a bulb containing an inert gas,a heater composed oftungsten and a refractory earth in combinationadapted to ionize the gas, an

bulb containing an inert gas, a heater adapt- -ed to ionize the gas, anelectrode of tungsten in parallel with one end of the heater, and asecond electrode of tungsten located, at least in part, between theheater and said first electrode.

EDWARD ALFRED GIMINGHAM.

Witnesses JOHN HENRY RUssoN, WALTER J. sKERTEN

